A lever escapement broadly answering the description given in the above paragraph is known and disclosed in the work entitled “La Montre: principes et méthodes de fabrication”, Scriptar Editions S. A., La Conversion, Lausanne 1993. This escapement is explained in pages 247 and 248 of said work. As may be understood upon reading this document the escapement further includes a second impulse pallet stone secured to the balance roller and cooperating with the escape wheel.
It is an object of the invention to provide an escapement structure that allows the impulses supplied by the pallet onto the balance wheel via the respective pallet stones to have for each alternation, a substantially identical amount of energy. The amount of energy is set to avoid any excessive rotational amplitude of the balance wheel thereby avoiding any risk of missing impulses and, therefore, limiting the energy wasted.